#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=2e5+1000;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
LL a[maxn];
LL dp[maxn];
LL pre[maxn];
map<LL,LL>map1;
int main(void)
{
  cin.tie(0);std::ios::sync_with_stdio(false);
  LL n;cin>>n;
  for(LL i=1;i<=n;i++) cin>>a[i];
  for(LL i=1;i<=n;i++) dp[i]=1,pre[i]=i;
  map1[a[1]]=1;
  for(LL i=2;i<=n;i++){
     if(map1.count(a[i]-1)){
        if(dp[i]<dp[map1[a[i]-1]]+1){
            dp[i]=dp[map1[a[i]-1]]+1;
            pre[i]=map1[a[i]-1];
        }
     }
     else dp[i]=max(dp[i],(LL)1);
     map1[a[i]]=i;
  }
  LL last=0;
  LL ans=0;
  for(LL i=1;i<=n;i++){
    if(ans<dp[i]){
        ans=dp[i];
        last=i;
    }
  }
  cout<<ans<<endl;
  vector<LL>v;
  while(pre[last]!=last){
    v.push_back(last);
    last=pre[last];
  }
  v.push_back(last);
  reverse(v.begin(),v.end());
  for(auto i:v){
    cout<<i<<" ";
  }
  cout<<"\n";
return 0;
}
